Radiator question.

[SnakeKack]

I noticed a leak of coolant from my car. It collects around the foam sponge strip along the top of the radiator. I looked all over for where the leak was coming from and could not find it until today. I pulled back the foam strip and looked at the top plastic piece of the radiator where the cap connects to. I squeezed the hoze and seen fluid slightly ooze out of a hair line crack in the plastic.

Now I was wondering, the radiator is in good condition but that small crack. Would I be able to replace just the plastic top(the piece that has the crack in it)? or maybe I can patch it with something? (silicone, sealant?)